Enhanced disease resistance in transgenic cabbage and tobacco expressing a glucose oxidase gene from Aspergillus niger

A GO gene from Aspergillus niger was constitutively expressed under the CaMV 35S promoter in transgenic cabbage and tobacco plants. During the vegetative stage, the transgenic tobacco grew normally, whereas the transgenic cabbage showed significant growth retardation even though GO activity was higher in tobacco. The transgenic cabbage was sterile, producing a few seeds only. Seed set was also decreased in transgenic tobacco and the germination rate of the seeds was markedly reduced. In transgenic tobacco, the basal level of PR-1a mRNA was very low, implying that the PR gene was not turned on by the constitutive production of H2O2. There was a small increase in the PR-1a mRNA when leaf segments were treated with a high concentration of glucose that caused massive cell death of the tissues. T1 tobacco plants showed delayed disease symptoms to Phytophthora nicotianae infection. T2 homozygous lines of transgenic cabbage were tested for resistance to black rot disease. The development of leaf lesions by Xanthomonas campestris pv. campestris was significantly reduced in transgenic cabbage and the disease tolerance was positively associated with the GO activity in leaves.